Variable Cam Timing Phaser Venting for Cold Start Oil Flow
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Solution Overview
Problem
Variable cam timing (VCT) mechanisms experience delays in performance due to high oil viscosity during cold engine startup, as they rely on hydraulic oil flow, which is slow at low temperatures, leading to delayed introduction of warm oil and reduced performance.
Innovation Solution
The VCT phaser is designed to enhance oil flow at low temperatures by allowing increased flow of cold oil to be replaced with warmer oil sooner, and reducing oil flow once operational, using a spool valve system that controls the venting and locking pin to facilitate faster warming and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the VCT mechanism limits oil consumption at high temperatures, then oil consumption is reduced, but oil exchange rate at low temperatures is also limited
Solution Approach 1:
The patent implements a dynamic oil flow control system that adjusts the oil exchange rate based on operating conditions. A control valve regulates oil flow to the VCT mechanism, allowing high flow rates during cold start to rapidly warm the oil and achieve target viscosity, then reducing flow rates during normal operation to limit oil consumption. This dynamic adjustment resolves the contradiction between rapid warming needs and oil consumption limitations.
Solution Approach 2:
The system changes the oil flow parameter dynamically based on temperature and viscosity conditions. During cold start, the control valve opens to allow maximum oil flow through the VCT mechanism, rapidly exchanging cold oil with warmer oil from the engine sump. Once the oil reaches operating temperature and viscosity, the valve closes to minimize oil consumption. This parameter change strategy enables the system to achieve both rapid warming and oil conservation at different operational phases.
2Ease of operation
If the VCT mechanism uses hydraulic oil flow, then it achieves variable cam timing control, but performance is delayed at low temperatures due to high oil viscosity
Solution Approach 1:
The patent implements preliminary warming action by directing oil flow through the VCT mechanism before full engine operation begins. The control system activates oil circulation through the phaser early in the cold start sequence, allowing the oil to begin warming and viscosity reduction before the engine reaches full operating conditions. This preliminary action reduces the overall warmup time and enables faster achievement of VCT performance.
Solution Approach 2:
The system uses hydraulic principles to force oil flow through the VCT mechanism despite high viscosity conditions. A control valve creates sufficient pressure differential to maintain oil circulation through the phaser during cold start, ensuring continuous oil exchange and heat transfer. This hydraulic approach overcomes the resistance of high-viscosity oil and maintains VCT functionality during the warmup phase.
3Productivity
If the VCT mechanism introduces warm oil quickly, then performance and emissions improve, but oil consumption increases
Solution Approach 1:
The patent implements periodic oil flow control where the system alternates between high-flow warmup mode and low-flow operation mode. During cold start, the control valve maintains high oil flow rates to rapidly warm the VCT mechanism and achieve target performance. Once the oil reaches operating temperature and viscosity, the valve transitions to a closed or partially closed state to minimize oil consumption during normal operation. This periodic switching between flow rates resolves the contradiction between performance achievement and oil conservation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces the time to introduce warm oil, enhancing VCT performance by optimizing oil flow through the phaser at both low and high temperatures, thus improving cold start emissions and drivability.
Implementation Method 1
when an engine is cold and the oil viscosity is high there is a delay in getting warm engine oil to flow through the variable cam timing (VCT) mechanism
Data Source
AI summary
The present invention increases cold temperature oil flow through the variable cam timing (VCT) phaser to reduce the amount of time it takes to replace this oil with warmer low viscosity oil and thereby improve performance. Furthermore the oil flow through the VCT phaser is reduced once the oil temperature reaches the minimum operating temperature for the VCT phaser to operate and the VCT phaser is commanded to move from the park position. Therefore, the VCT phaser is charged with hot engine oil and is commanded to move from the parked position. The VCT phaser reduces oil flow through the phaser at high oil temperatures and low oil viscosity while adding the benefit of increased oil flow through the phaser at low oil temperatures and high oil viscosity to facilitate getting warmer oil into the VCT phaser sooner for increased VCT performance.